Microminiature field emitters may be used as electron sources in a variety of microelectronic or MEMS devices utilized in flat panel displays, automobiles, head wearable displays, heads up displays, outdoor signage, etc. One such use of a MEMS device is as an image intensifier for night vision goggles, which enables the reduction of the size and weight of the goggles.
The image intensifiers typically utilize high voltage (e.g., 4,000-6,000 volts) vacuum MEMS devices, which may be constructed from panels or plates of various materials that are spaced from one another. The space between the two plates may be evacuated and sealed by a spacing structure disposed along the outer or annular regions of each of the plates. One of the plates may serve as the cathode of the device, while the other plate may serve as the anode of the device. Thus, when a voltage is applied across the plates, the cathode plate accelerates electrons through the spacing toward the anode plate. The anode plate may include a phosphor screen that is impacted with electrons from the cathode, causing the phosphors of the screen to luminesce and emit light through the anode plate.
Because the type of MEMS devices utilized in image intensifiers requires a high voltage, and because these MEMS devices typically have cesium deposited in the vacuum, the surface path length (i.e., the path along the inner surface of the spacing structure between the cathode plate and the anode plate) must be 6-10 times the length of the vacuum gap (i.e., the spacing between the cathode plate and the anode plate). If the path length is not long enough, the MEMS device may run dark or leakage current, which can inhibit performance of the MEMS device.
In addition, typical high voltage MEMS devices such as image intensifiers are also subject to flashover at various surfaces. This can become catastrophic to the MEMS device, ultimately resulting in failure or destruction of the MEMS device. For example, electrons that are created at the triple junction of the MEMS device (e.g., the intersection of the upper plate, the spacing structure, and the vacuum) can be accelerated by the field strength in the vacuum gap to strike a vertical surface of the spacing structure. The impact of electrons on the vertical surfaces of the spacing structure creates a cascading process of electrons, which results in multipacting, and can catastrophically destroy the device. Furthermore, electrons that backscatter from the phosphor screen of the anode plate may also impact the vertical surface of the spacing structure to also cause multipacting.
Therefore, what is needed is a MEMS device with a spacing structure that increases the surface path length between the cathode plate and the anode plate, while minimizing the vacuum gap between the cathode plate and anode plate. Furthermore, what is also needed is a spacing structure of a MEMS device that minimizes or eliminates the occurrences of multipacting from electrons formed at the triple junction of the MEMS device. What is also needed is a spacing structure of a MEMS device that reduces the likelihood that electron backscatter from a phosphor screen or anode surface results in multipacting.